In semiconductor manufacturing, thermal processes are commonly used to melt, anneal, crystallize, and activate dopants in semiconductor substrates. High power levels are generally used to process semiconductor substrates, and lasers are frequently used to achieve the high power levels. Lasers produce coherent light that has a non-uniform spatial distribution of energy. Depending on the structure of the lasing medium, the distribution will have local maxima and minima that result in higher and lower energy intensity, which leads to non-uniform processing of substrates. Moreover, the shape of the laser energy field is often different from the desired shape of the processing region.
Much work has been devoted to improving the uniformity of a laser energy field and adapting its shape to a desired geometry, with improvement roughly keeping pace with the shrinking scale of semiconductor devices. Further improvement is still needed, however, as the trend of miniaturization continues.